docs(release): static versioned README download links

The releaseAssetNamePattern input was never honored by tauri-action —
the draft release got default versioned asset names (Gridline_0.7.5_*.dmg,
Gridline-0.7.5-1.x86_64.rpm, ...), so the version-free releases/latest
links in the README would 404. Per user decision, drop the dynamic
scheme: both README download tables now link statically to the v0.7.5
assets, with a MAINTENANCE comment and an AGENTS.md checklist entry
reminding to bump both tables on each release. Remove the dead
releaseAssetNamePattern config from release.yml.

AGENTS.md

@@ -156,7 +156,7 @@ Cut a release from the **`prod`** branch (never feature branches) by tagging it
 **Before tagging**, keep everything in sync:
 - Version number across `package.json`, `src-tauri/Cargo.toml`, and `src-tauri/tauri.conf.json`
 - `src/lib/version.test.ts` and `src/lib/docs-coverage.test.ts` if they assert the version
-- **README download links stay version-free** — both download tables (top **Download** section + **Which file should I download?**) link via GitHub's `releases/latest/download/<file>` redirect, which only works because `release.yml` sets `releaseAssetNamePattern` to a version-free pattern (`[name]_[platform]_[arch][setup][ext]`). Do NOT re-add the version to these filenames on release.
+- **README download links are static (versioned)** — both download tables (top **Download** section + **Which file should I download?**) link directly to the release-tag assets (`releases/download/v0.7.5/<file>`). tauri-action uses default versioned asset names (`Gridline_<ver>_aarch64.dmg`, `Gridline-<ver>-1.x86_64.rpm`, etc.) — update BOTH tables to the new names on every release (see the MAINTENANCE comment in README.md).
 - **Bundled pg tools:** `tauri.conf.json` `bundle.resources` lists `resources/pg_tools/*`; the `release.yml` matrix builds/downloads + checksum-verifies the static binaries before the Tauri build step.
 
 ### Adding a Tauri Command